Condensed Consolidated Statements of Changes in Stockholders' Equity Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Millions, $ in Millions	Total	Common Stocks	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Adjustments to Additional Paid in Capital [Abstract]
Additional Paid in Capital			$ 8,973
Retained Earnings (Accumulated Deficit) [Abstract]
Retained Earnings (Accumulated Deficit)				$ 12,550
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (329)					$ (329)
Adjustments to Additional Paid in Capital, Share-based Compensation, Employee Stock Purchase Program, Requisite Service Period Recognition			(124)
Allocated Share-based Compensation Expense			19
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation			24
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs			7
Net Income (Loss) Attributable to Parent	323			323
Dividends, Common Stock, Cash				84
Treasury Stock, Value at Dec. 31, 2015					$ (3,557)
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Treasury stock acquired					(350)
Issuance of shares under incentive and stock compensation plans from treasury stock					(125)
Return of shares under incentive and stock compensation plans and other to treasury stock	(10)				(46)
Adjustments to Additional Paid in Capital, Stock Issued, Own-share Lending Arrangement, Issuance Costs					7
Treasury Stock, Value at Mar. 31, 2016					(3,821)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), Net of Tax	583					583
Common Shares Outstanding, at beginning of period (in thousands) at Dec. 31, 2015		401,821.0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Treasury stock acquired		(8,394.0)
Issuance of shares under incentive and stock compensation plans		3,069.0
Return of shares under incentive and stock compensation plans and other to treasury stock		(1,066.0)
Issuance of Shares for Warrant Exercise		173.0
Common Shares Outstanding, at end of period (in thousands) at Mar. 31, 2016		395,603.0
Preferred Stock, Including Additional Paid in Capital [Abstract]
Common Stock, Value, Issued		$ 5
Adjustments to Additional Paid in Capital [Abstract]
Additional Paid in Capital			8,885
Retained Earnings (Accumulated Deficit) [Abstract]
Retained Earnings (Accumulated Deficit)				12,789
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax	254					254
Total stockholders' equity	18,112
Common Stock, Value, Issued	4
Additional Paid in Capital	5,247		5,247
Retained Earnings (Accumulated Deficit)	13,114			13,114
Accumulated Other Comprehensive Income (Loss), Net of Tax	(337)					(337)
Total stockholders' equity	16,903
Adjustments to Additional Paid in Capital, Share-based Compensation, Employee Stock Purchase Program, Requisite Service Period Recognition			(66)
Allocated Share-based Compensation Expense			36
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation			0
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs			40
Net Income (Loss) Attributable to Parent	378			378
Dividends, Common Stock, Cash				86
Treasury Stock, Value at Dec. 31, 2016	(1,125)				(1,125)
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Treasury stock acquired					(325)
Issuance of shares under incentive and stock compensation plans from treasury stock					(72)
Return of shares under incentive and stock compensation plans and other to treasury stock	(26)				(33)
Adjustments to Additional Paid in Capital, Stock Issued, Own-share Lending Arrangement, Issuance Costs					40
Treasury Stock, Value at Mar. 31, 2017	(1,371)				$ (1,371)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), Net of Tax	$ 130					130
Common Shares Outstanding, at beginning of period (in thousands) at Dec. 31, 2016		373,949.0
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Treasury stock acquired	(6.7)	(6,709.0)
Issuance of shares under incentive and stock compensation plans		1,690.0
Return of shares under incentive and stock compensation plans and other to treasury stock		(674.0)
Issuance of Shares for Warrant Exercise		940.0
Common Shares Outstanding, at end of period (in thousands) at Mar. 31, 2017		369,196.0
Preferred Stock, Including Additional Paid in Capital [Abstract]
Common Stock, Value, Issued	$ 4	$ 4
Adjustments to Additional Paid in Capital [Abstract]
Additional Paid in Capital	5,177		$ 5,177
Retained Earnings (Accumulated Deficit) [Abstract]
Retained Earnings (Accumulated Deficit)	13,406			$ 13,406
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(207)					$ (207)
Total stockholders' equity	$ 17,009